JPH0911043A - Electric discharge machining method and electric discharge machine - Google Patents

Abstract

(57) [Summary] [Object] To provide an electric discharge machining method capable of accurately controlling the electric discharge machining gap based on machining energy. When a discharge is generated between the wire electrode 2 and the work piece 1, a normal discharge detection circuit 20, a short detection circuit 21, and a leak detection circuit 22 indicate a normal discharge, a short-circuit state and a leak state from a voltage waveform between electrodes. The normal discharge frequency fd, the short-circuit frequency fs, and the leak discharge frequency fl are obtained through the fd counter 30, fs counter 31, and fl counter 32.
Send to 0. The CPU 40 calculates machining energy from the data and preset machining efficiency, and sends a position command to the position servo control circuit 41 based on the machining energy. The position servo control circuit 41 drives the servo motors 5 and 6 based on the position command to optimize the relative position between the workpiece 1 and the wire electrode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method and an electric discharge machining apparatus, and more particularly to an electric discharge machining method and an electric discharge machining apparatus capable of performing stable servo feed machining even in an in-corner portion and an out-corner portion in finishing machining or the like. Regarding

[0002]

2. Description of the Related Art In electric discharge machining, a voltage pulse is applied between an electrode and a workpiece (machining gap) to generate an electric discharge between them, and a predetermined energizing time (Ton) and rest time (Toff). Is repeated to process the work piece. Generally, the time from the application of a voltage pulse to the start of discharge is the no-load voltage application time (hereinafter simply referred to as "no-load time").
That is, the time from the start of discharge to the end of discharge is called energization time (Ton), and the time from the end of discharge to application of the next voltage pulse is called rest time (Toff).

In order to maintain stable discharge, it is necessary to control (servo feed) the relative feed rate between the electrode and the workpiece. Conventionally, this type of feed rate control appears in the machining gap. A method is known in which the voltage between contacts (pulse voltage) is averaged using a filter circuit, and the feed speed is controlled so that the average voltage becomes a predetermined value. Further, a method of directly counting the no-load time using a clock pulse or the like and controlling the feed rate based on the no-load time (Japanese Patent Laid-Open No. 2-1
No. 09633) and a discharge frequency are detected, a no-load time is calculated from the discharge frequency, and a feed speed is controlled based on the no-load time (JP-A-6-065732).

[0004]

Generally, in the finish machining of electric discharge machining, the electric discharge frequency is high and the no-load time is very short in many cases. Therefore, in the method of detecting the average voltage of the voltage between contacts using a filter circuit, it is difficult to distinguish between a short-circuit state caused by machining waste and a state in which the no-load time is extremely short, and stable servo feed is required. Was difficult.

On the other hand, even in the method of detecting or calculating the no-load time and controlling the feed rate based on the no-load time, it is not possible to distinguish between a short-circuit state and a state in which the no-load time is extremely short. It has been difficult to perform optimum servo feed when the machining amount changes extremely, such as.

The present invention has been made in view of the conventional problems as described above, and it is possible to accurately control the machining gap based on the machining energy, and particularly to perform stable servo feed machining even in finishing. It is an object of the present invention to provide an electric discharge machining method and an electric discharge machining apparatus capable of performing the above.

[0007]

According to the first aspect of the present invention,
A voltage pulse is intermittently applied according to a preset energization time and a dwell time in a machining gap between the machining electrode and the workpiece to generate an electric discharge, and the machining electrode and the workpiece are relatively moved. In the electrical discharge machining method for machining a workpiece by, by detecting the electrical discharge state during machining and distinguishing into a plurality of electrical discharge states, detecting a plurality of electrical discharge frequencies according to the plurality of electrical discharge states, the plurality of electrical discharge states According to the above, a plurality of machining efficiencies are set in advance, and a machining energy is calculated based on the plurality of electric discharge frequencies and the machining efficiencies,
The relative position between the machining electrode and the workpiece is controlled based on the machining energy.

According to a second aspect of the present invention, the processing energy is calculated by a sum of products of the plurality of discharge frequencies and the processing efficiency corresponding to each of them.

According to a third aspect of the present invention, the relative position between the machining electrode and the workpiece is controlled, and the relative movement between the machining electrode and the workpiece is controlled according to the relative speed determined by the machining energy. It is characterized by including controlling.

According to a fourth aspect of the present invention, the discharge state during machining is detected and the plurality of discharge states are distinguished. In a normal normal discharge state, a short circuit occurs between the machining electrode and the workpiece. It is characterized in that it is identified as a short-circuited state or a leaking state that is leaking.

According to a fifth aspect of the present invention, the discharge state during machining is detected and the plurality of discharge states are distinguished. The discharge start voltage is stored every time the intermittent voltage pulse is applied, and the discharge start voltage is stored. The discharge state between the machining electrode and the workpiece is identified based on the stored data of the discharge starting voltage.

According to a sixth aspect of the present invention, a voltage pulse is intermittently applied to a machining gap between the machining electrode and the workpiece in accordance with a preset energization time and rest time to generate an electric discharge, and at the same time, the machining is performed. In an electric discharge machining apparatus for machining a workpiece by moving an electrode and the workpiece relative to each other, a means for detecting an electric discharge state during machining and discriminating into a plurality of electric discharge states, and a plurality of electric discharge states to be identified. Means for detecting a plurality of discharge frequencies, means for setting a plurality of machining efficiencies according to the plurality of discharge states in advance, and means for calculating a machining energy based on the plurality of discharge frequencies and the machining efficiency A position control means for controlling the relative position of the machining electrode and the workpiece based on the calculated machining energy is provided.

The invention according to claim 7 is characterized in that the energization time and / or the rest time in the invention according to claim 6 are variably set according to a machining state during machining.

According to an eighth aspect of the invention, the means for setting the machining efficiency in the invention according to the sixth aspect comprises a storage means for storing a plurality of preset machining efficiencies, and the calculating means comprises: The processing efficiency is read from the storage means to calculate the processing energy.

According to a ninth aspect of the present invention, the calculating means in the sixth aspect of the present invention calculates the processing energy by the product sum of the plurality of discharge frequencies and the processing efficiency corresponding to each of them. It is a feature.

According to a tenth aspect of the invention, the position control means in the sixth aspect of the invention controls the relative movement between the machining electrode and the workpiece according to the relative speed determined by the machining energy. It is characterized by.

According to an eleventh aspect of the present invention, the identifying means in the sixth aspect of the invention determines that the discharge state between the machining electrode and the workpiece is a normal normal discharge state, the machining electrode and the workpiece. The present invention is characterized in that it distinguishes between a short-circuited state in which a short circuit is made between the workpiece and a leaked state in which the workpiece is leaking.

According to a twelfth aspect of the present invention, the identifying means stores a discharge start voltage each time the intermittent voltage pulse is applied, and the discharge state is stored based on the stored discharge start voltage data. It is characterized by identifying.

[0019]

In the electric discharge machining method of the present invention, the voltage gap is intermittently applied to the machining gap between the machining electrode and the object to be machined according to the preset energization time and rest time, and electric discharge is generated. When machining the workpiece by moving the machining electrode and the workpiece relative to each other, it detects multiple discharge states (normal discharge, short circuit, leak, etc.) during machining and the discharge frequency of each of these discharge states. Then, a pseudo machining energy based on the machining efficiency and the discharge frequency preset according to each discharge state is calculated, and the relative position between the electrode and the workpiece is controlled based on the calculated machining energy. It was done like this.

As described above, instead of controlling the inter-electrode gap by the average voltage or the no-load time, it is possible to estimate the machining energy from the discharge state and control the inter-electrode gap while monitoring it. Electric discharge machining by feeding becomes possible.

The processing energy is calculated by summing the products of the plurality of discharge frequencies and the processing efficiency corresponding to each of them.

With respect to controlling the relative position between the machining electrode and the workpiece, the relative movement between the machining electrode and the workpiece is controlled according to the relative speed determined by the machining energy.

Regarding the detection of the discharge state during machining and the identification of the plurality of discharge states, a normal normal discharge state, a short state in which the machining electrode and the workpiece are short-circuited or Identify the leaked state.

Further, regarding the detection of the discharge state during machining and the identification of the plurality of discharge states, the discharge start voltage is stored every time the intermittent voltage pulse is applied, and the stored discharge start is stored. The discharge state between the machining electrode and the workpiece is identified based on the voltage data.

According to the electric discharge machining apparatus of the present invention, means for detecting the electric discharge state during machining and discriminating into a plurality of electric discharge states, and means for detecting a plurality of electric discharge frequencies corresponding to the plural electric discharge states to be discriminated. A means for setting a plurality of machining efficiencies according to the plurality of discharge states in advance, a means for calculating a machining energy based on the plurality of discharge frequencies and the machining efficiency, and a machining electrode based on the calculated machining energies. And the position control means for controlling the relative position of the workpiece and the workpiece, the electric discharge machining method that exhibits the above-described action by the operation of these means can be realized.

In this case, the energization time and / or the rest time are variably set according to the processing state during processing.

When calculating the processing energy, the calculating means reads a plurality of preset processing efficiencies from the storage means and calculates the processing energy based on the read processing efficiencies.

Further, the calculating means calculates the processing energy by the product sum of the plurality of discharge frequencies and the processing efficiency corresponding to each of them.

The position control means, when controlling the relative position between the machining electrode and the workpiece, moves the machining electrode and the workpiece relative to each other in accordance with the relative speed determined by the machining energy. To control.

Furthermore, the detecting means detects a discharge state during machining and distinguishes between the plurality of discharge states, a normal normal discharge state, a short circuit between the machining electrode and the workpiece. The short-circuited state and the leaked state that are leaking are identified.

The identifying means stores a discharge start voltage each time the intermittent voltage pulse is applied and detects the discharge state during machining and distinguishes the discharge state from the plurality of discharge states. Each of the discharge states is identified based on the generated discharge start voltage data.

By the operation of each means of such an electric discharge machining apparatus, the machining energy can be estimated from the electric discharge state and the gap between the electrodes can be controlled while monitoring, so that electric discharge machining by more accurate and stable servo feeding can be performed. The electric discharge machining method of the present invention can be realized.

[0033]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a wire electric discharge machine as an embodiment of the electric discharge machine of the present invention.

In the wire electric discharge machine shown in FIG. 1, the relative positions of the workpiece 1 and the wire electrode 2 are controlled by the servomotors 5 and 6 which form the position control means, and the workpiece 1 and the wire electrode 2 are controlled. A machining gap is formed between the and. The wire electrode 2 is stretched between the guides 3 and 3, and a DC power supply 7 and a switching element (transistor) are provided in the processing gap.
Intermittent voltage pulses are applied through 8, resistor 9, and power supply 4.

The normal discharge detection circuit 20, the short circuit detection circuit 21, and the leak detection circuit 22 shown in FIG. 1 indicate the discharge state from the voltage waveform between electrodes when a voltage pulse is applied between the electrode 2 and the workpiece 1. This is the detection circuit. A normal discharge pulse is output from the normal discharge detection circuit 20 when the normal discharge is performed, and a short pulse is output from the short detection circuit 21 when the discharge is not performed and the battery is in a short state.
Further, the leak detection circuit 22 outputs a leak discharge pulse when discharge occurs when the voltage between the electrodes is relatively low.

The fd counter 30, fs counter 31, and fl counter 32 shown in FIG. 1 respectively count the normal discharge pulse, the short pulse, and the leak discharge pulse to obtain the normal discharge frequency fd, the short frequency fs, and the leak discharge frequency fl. , C constituting the means for calculating these
The PU 40 converts the data into fd data, fs data, and fl data, which are output to the CPU 40.

In the above embodiment, the fd counter 30,
The normal discharge frequency fd, the short-circuit frequency fs, and the leak discharge frequency fl are obtained by the fs counter 31 and the fl counter 32. However, the present invention is not limited to this. For example, the fd counter 30, the fs counter 31, and the fl counter 32 each have a normal discharge pulse. , Short pulse and leak discharge pulse are counted, and these count values are read by the CPU 40 at every predetermined sampling period,
The CPU 40 may calculate the normal discharge frequency fd, the short frequency fs, and the leak discharge frequency fl based on the count value and the sampling cycle.

The CPU 40 is a control circuit including a plurality of CPUs and a memory as a storage means, and performs various calculations based on fd data, fs data, fl data and other data, as will be described later, and the electrodes are operated. A position command for controlling the gap length between 2 and the workpiece 1 is output to the position servo control circuit 41 such as a numerical controller. The output of the position servo control circuit 41 is connected to the motors 5 and 6, and the motors 5 and 6 are mechanically connected to the workpiece 1 (or the electrode 2) to control the relative positions of the workpiece 1 and the electrode 2. ing. In addition, the memory includes the energization time Ton and the rest time Tof.
Various processing conditions such as f are set and stored by a predetermined input means.

The pulse train generation circuit 42 fetches various pulse data such as preset energization time Ton and rest time Toff from the CPU 40, generates a predetermined pulse train, and outputs this pulse train to the isolation amplifier 10 for switching. The element 8 is turned on and off. That is,
As shown in FIG. 3, the pulse train turns on the switching element 8 for the energization time Ton from the discharge start signal, and then turns off the switching element 8 for the rest time Toff. After Toff, the switching element 8 is turned on again.

FIG. 2 is a block diagram showing the configurations of the normal discharge detection circuit 20, the short circuit detection circuit 21, and the leak detection circuit 22. As shown in FIG. 2, the normal discharge detection circuit 20 detects the voltage between the workpiece 1 and the electrode 2 as a resistance R.
1, the differential amplifier 61 which receives the voltage divided by R2, and the divided voltage between contacts with a predetermined reference voltage Vd (variably settable) are compared, and when the voltage becomes equal to or higher than the reference voltage Vd, it is high (logic High).
A comparator 62 that outputs a signal and an output of this comparator 62 are differentiated to output a normal discharge pulse to the fd counter 3
And a differentiating circuit 63 for outputting 0.

In FIG. 2, R3 and R4 are input resistors and 64
Is a feedback impedance of the impedance Z, and 65 is a ground impedance of the impedance Z.

On the other hand, the short circuit detection circuit 21 comprises a comparator 71, a flip-flop (R-SFF) 72, an AND gate 73 and an inverter 74, which are connected as shown in FIG.

The R (reset) terminal of the flip-flop 72 and one input terminal of the gate 73 are connected to the pulse train generation circuit 42, respectively. Pulse train generation circuit 4
2 outputs a reset signal to the flip-flop 72 and a flip-flop (R-SFF) 82 of the leak detection circuit 22 described later, for example, immediately before applying a voltage pulse between the electrodes. Further, the pulse train generation circuit 42 sends a short check pulse (high signal) to the AND gate 73 after a lapse of a predetermined short detection time Ts from the application of the voltage pulse between electrodes.
Is output.

The comparator 71 compares the output voltage of the differential amplifier 61 of the normal discharge detection circuit 20 with the short reference voltage Vs (variably settable), and the output voltage of the differential amplifier 61 is lower than the short reference voltage Vs. When it is low, a low signal is output to the set terminals of the inverter 74 and the flip-flop 72. The inverter 74 is
The low signal from the comparator 71 is inverted and a high signal is output to the AND gate 73. At this time, since the set terminal of the flip-flop 72 is set to low by the low signal from the comparator 71, the flip-flop 7
A high signal is sent from the complementary terminal 2 to the AND gate 73, and the pulse train generation circuit 42 applies a predetermined short circuit detection time Ts after the application of the voltage pulse between electrodes,
Since a short check pulse (high signal) is output to the AND gate 73, the AND gate 73 determines from these signals that the AND gate 73 is in the short state, the AND gate 73 is opened, and the short pulse is output to the fs counter 31.

Furthermore, when the discharge occurs before the predetermined short-circuit detection time Ts has elapsed from the application of the inter-electrode voltage pulse, it is not in a short-circuit state, and therefore the output of the differential amplifier 61 is output even once after the application of the inter-electrode voltage pulse. When the voltage becomes higher than the short circuit reference voltage Vs, the comparator 71 outputs a high signal to the inverter 74, the set terminal of the flip-flop 72 and the differentiating circuit 81 described later. This allows
Since the flip-flop 72 set terminal is set to high, a low signal is sent from the complementary terminal of the flip-flop 72 to the AND gate 73, and the AND gate 73 is closed. As a result, the AND gate 73 to the fs counter 31
Output of pulse to is prohibited. In short, the short-circuit detection circuit 21 outputs a short pulse when discharge does not occur after the short-circuit detection time Ts has elapsed and the voltage between contacts is equal to or less than the short-circuit reference voltage Vs.

Further, the leak detection circuit 22 includes a differentiating circuit 8
1, a flip-flop 82 and an AND gate 83, which are connected as shown in FIG. The differentiating circuit 81 differentiates the output of the logic high from the comparator 71 of the short circuit detecting circuit 21 and outputs all discharge pulses other than the short circuit. That is, in the differentiating circuit 81, when the discharge is generated before the predetermined short circuit detection time Ts elapses from the application of the voltage pulse between electrodes, and the output voltage of the differential amplifier 61 becomes higher than the short circuit reference voltage Vs even once. Then, all discharge pulses other than short circuit are output to the AND gate 83.

Flip-flop 8 of leak detection circuit 22
2 is set when the output of the comparator 62 of the normal discharge detection circuit 20 is logic high, and stores the normal discharge state. At this time, the output of the complementary terminal of the flip-flop 82 becomes a logic low, and the AND gate 83 is closed. Therefore, the AND gate 83 outputs only the leak discharge pulse obtained by removing the normal discharge pulse from the total discharge pulse output from the differentiating circuit 81 to the fl counter 32. The leak discharge frequency fl may be calculated based on the total discharge pulse and the normal discharge pulse instead of directly counting the leak discharge pulse.

Next, an electric discharge machining method using the electric discharge machine shown in FIG. 1 will be described.

When a discharge is generated between the electrode 2 and the workpiece 1, the voltage waveform between the electrodes changes as shown in FIG. 3 (A). That is, the transistor 8 is turned on by the pulse train generation circuit 42, and the no-load time tw of FIG.
After the passage of d, the discharge has started. The normal discharge detection circuit 20 detects normal discharge, which is discharge after the voltage between contacts exceeds the normal discharge reference voltage, and the energization time Ton from the start of discharge.
After a lapse of time, the transistor 8 is turned off and the discharge ends. After that, when the rest time Toff has elapsed, the transistor 8 is turned on again, and the same operation is repeated thereafter.

However, as shown in FIG. 3B, when the voltage between contacts does not reach the predetermined reference value even after the short-circuit detection time Ts has elapsed since the discharge pulse was applied between the machining gaps, it is judged as a short circuit. After the determination, a short-circuit voltage is applied, and the transistor 8 is controlled by the energization time Tons and the rest time Toffs at the time of short-circuit, and a short-circuit current flows. The values of Tons and Toffs are arbitrarily set according to the processing conditions and stored in advance in the CPU 40.

FIG. 3C shows a leak state in which the discharge is not short-circuited but the discharge start does not reach the predetermined normal discharge reference voltage and discharge is generated. In the present embodiment, the start of discharge is shown to occur between the normal discharge reference voltage and the short reference voltage, but it may be distinguished into a plurality of states. For example, each time a discharge pulse is applied, the discharge start voltage may be stored, its analog value may be converted into digital data, and the CPU 40 may read the data.

Now, the normal discharge frequency fd is sent from the fd counter 30, the short frequency fs is sent from the fs counter 31, and the leak discharge frequency fl is sent from the fl counter 32 to the CPU 40 as data.

Generally, the processing energy of each discharge pulse is different. When the processing energy (processing efficiency) per pulse of the normal discharge pulse, the short pulse and the leak discharge pulse is Kd, Ks and Kl, respectively, the processing energy Pd per unit time is Pd = fd × Kd +
It can be represented by fs × Ks + fl × Kl.

When the plate thickness of the workpiece 1 is L (constant) and the processing speed is Fd, it can be expressed as Fd = Pd / L.
Therefore, the relative movement speed command between the workpiece 1 and the electrode 2, that is, the processing speed command Fp is set to CP so that Fp = Fd.
U40 outputs a position command to the position servo control circuit 41.

When the plate thickness of the work piece 1 is not constant, the target processing energy Po set by the material of the work piece 1 and the processing conditions is set in advance, and the CPU 40 sets Po = Pd so that Po = Pd. A position command may be output to the position servo control circuit 41. In the present embodiment, the plate thickness of the work piece 1 is assumed to be constant.

The CPU 40 receives the normal discharge frequency fd, the short frequency fs, and the leak discharge frequency f from the fd counter 30, the fs counter 31, and the fl counter 32, respectively.
l (FIG. 4, step S1) Further, L, Kd, Ks, and Kl are read from the memory (step S1).
2), Pd = fd × Kd + fs × Ks + fl × Kl is calculated to calculate the estimated machining energy Pd (step S3), and the estimated machining speed Fd is calculated based on the equation Fd = Pd / L (step S3). S4). Then Fp = F
The relative movement speed command Fp is obtained based on the equation of d (step S5).

The CPU 40 outputs a position command for controlling the gap length of the electrode 2 and the workpiece 1 to the position servo control circuit 41 based on the calculated relative movement speed command.
The position servo control circuit 41 drives the motors 5 and 6 according to the given position command to control the gap length of the electrode 2 and the workpiece 1.

The present invention is not limited to this embodiment, and the electric discharge machine is not limited to the wire electric discharge machine but can be applied to a die-sinking electric discharge machine.

[0060]

As described above, according to the present invention, the electric discharge state during machining is discriminated into a plurality of states, the electric discharge frequency of each of them is detected, and the machining efficiency corresponding to each machining state is preset. Since the machining energy is calculated from the discharge frequency and machining efficiency, and the relative position of the electrode and the workpiece is controlled based on that machining energy, machining pulses with significantly different machining energy from normal discharge such as shorts and leaks occur. It is possible to provide an electric discharge machining method for performing stable servo feed machining even in machining of an inner corner portion or the like.

Further, according to the present invention, by the constitution using the means for identifying the discharge state, the means for detecting the discharge frequency, the means for setting the machining efficiency, the means for calculating the machining energy and the position control means, It is possible to provide an electric discharge machine that can surely realize an electric discharge machine method that produces an effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an electric discharge machine of the present invention.

2 is a block diagram showing a configuration of a normal discharge detection circuit, a short circuit detection circuit, and a leak detection circuit in the electric discharge machine shown in FIG.

FIG. 3 is a waveform diagram showing the voltage between contacts during normal discharge, short circuit, and leakage.

FIG. 4 is a flowchart showing a CPU operation for calculating a processing speed command.

[Explanation of symbols]

 1 Workpiece 2 Wire Electrode 3 Guide 4 Electric Supply 5 Servo Motor 6 Servo Motor 7 DC Power Supply 8 Switching Element 9 Resistor 20 Normal Discharge Detection Circuit 21 Short Circuit Detection Circuit 22 Leak Detection Circuit 30 fd Counter 31 fs Counter 32 fl Counter 40 CPU 41 Position servo detection circuit 42 Pulse train control circuit

Claims (12)

[Claims] 1. An electric discharge is generated by intermittently applying a voltage pulse to a machining gap between a machining electrode and a workpiece in accordance with a preset energization time and rest time, and at the same time, the machining electrode and the workpiece are In an electric discharge machining method for machining a workpiece by relatively moving, a discharge state during machining is detected and identified into a plurality of discharge states, and a plurality of discharge frequencies corresponding to the plurality of discharge states are detected, A plurality of machining efficiencies are set in advance according to the plurality of electric discharge states, a machining energy is calculated based on the plurality of electric discharge frequencies and the machining efficiency, and a relative between the machining electrode and the workpiece based on the machining energy. An electric discharge machining method characterized by controlling a position. 2. The electric discharge machining method according to claim 1, wherein the machining energy is calculated by a sum of products of the plurality of discharge frequencies and the machining efficiency corresponding to each of the plurality of discharge frequencies. 3. Controlling relative positions of a machining electrode and a workpiece, wherein relative movement of the machining electrode and the workpiece is controlled according to a relative speed determined by the machining energy. The electric discharge machining method according to claim 1. 4. A normal normal discharge state, a short-circuit state in which the machining electrode and the workpiece are short-circuited, or a state in which a discharge state during machining is detected and the plurality of discharge states are distinguished, The electrical discharge machining method according to claim 1, wherein the leakage state is identified. 5. A discharge start voltage is stored every time the intermittent voltage pulse is applied, and the discharge start voltage stored in the discharge start voltage is detected every time the intermittent voltage pulse is applied. The electrical discharge machining method according to claim 1, wherein the electrical discharge state between the machining electrode and the workpiece is identified based on the data of (1). 6. A machining gap between the machining electrode and the workpiece is intermittently applied with a voltage pulse in accordance with a preset energization time and rest time to generate an electric discharge, and at the same time, the machining electrode and the workpiece are separated from each other. In an electric discharge machine for machining a workpiece by moving the workpiece relative to each other, a means for detecting the electric discharge state during machining and discriminating into a plurality of electric discharge states, and a plurality of electric discharge frequencies corresponding to the plural electric discharge states to be identified are provided. A means for detecting, a means for setting a plurality of machining efficiencies according to the plurality of discharge states in advance, a means for calculating a machining energy based on the plurality of discharge frequencies and the machining efficiency, and a calculated machining energy An electric discharge machining apparatus comprising: a position control unit that controls a relative position between a machining electrode and a workpiece based on the machining electrode. 7. The electric discharge machining apparatus according to claim 6, wherein the energization time and / or the pause time are variably set according to a machining state during machining. 8. The processing efficiency setting means includes a storage means for storing a plurality of preset processing efficiencies, and the calculation means calculates the processing energy from the storage means. The electric discharge machining apparatus according to claim 6, wherein the efficiency is read. 9. The electric discharge machining apparatus according to claim 6, wherein the calculating means calculates machining energy by summing products of the plurality of discharge frequencies and the machining efficiencies corresponding to the respective discharge frequencies. 10. The electric discharge machining apparatus according to claim 6, wherein the position control means controls the relative movement of the machining electrode and the workpiece according to the relative velocity determined by the machining energy. 11. The identifying means determines a discharge state between a machining electrode and a workpiece as a normal normal discharge state, a short state in which the machining electrode and the workpiece are short-circuited, and 7. The electric discharge machine according to claim 6, wherein the electric discharge machine is identified as a leaked state. 12. The identifying means stores a discharge start voltage each time the intermittent voltage pulse is applied, and identifies the discharge state based on the stored discharge start voltage data. The electric discharge machine according to claim 6.